Feed-water and steam heater for steam-boilers.



No. 688,402. Patemanemlo, I901. m; n; FORNEY.

FE ED WATER AND STEAM HEAT- ER FOR STEAM BOILERS.

(Application filed Julie 19, 1901.

l5 Sheets-Sheet (NoJlodeL) WITNESSES H N R 0 w A n1: NORRIS PETERS co.PHOTOLITHQ, mammal. a

Patented Dec. l0, I901.

M. N. .FORNEY.

FEED WATER AND STEAM HEATER FOR STEAM BOILERS.

(Application filed lane 19, 1901.)

I5 Sheets-Sheat 2.

(No Model.)

WITNESSES:-

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m: nunms PETERS to, woruufpn. wnsumm'un. o. c.

Nu. 688,402. Patented Dec. l0, 190i.

7 M. NpFOBNEY. I FEED WATER AND STEAM HEATER FOR STEAM BOILERS.

(Applicatidn flied June 19, 1901,

(No Model.) l5 Sheets-Sheet 3.

o SSS? INVENTOR WITNESSES:

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No. 688,402. Patented Dec. lo, |9o|.'

M.-N.'FORNEY. FE ED WATER AND STEAM HEATER FOR STEAM BOILERS.

(Application am June 19, 1901. (No Model.) l5 SheetsvSheet 4.

Q 99 996 Q QQMQQHQ m Q o O Mm .o W @Wowfivmv Mu PQ n o M 69 z W N w L. mw @559 mom M "I" m I a No. 688,402. Patented D60; l0, l90l.

M. N. FORNEY.

FEED WATER AND STEAM HEATER FOR STEAM BOILERS.

(Application filed June 19, 19011 (No Model.) l5 Shaets-Sheot 5.

INVENTOR V I I WITNESSES:

ATTO R N EY Tu: Nonms PETERS cu. PHOTO-UTHO WASHINGTON, n c.

No. 688,402. Patented Dec. 10, I90l. M. N. FDRNEY.

FEED WATER AND STEAM HEATER FUR STEAM BOILERS.

(Application filed June 19, 1901.)

(No Model.) l5 SheatsSheat 6.

WITNESSES; INVENTGR ATTORNE'Y Patented Dec. I0, I90.

M. N. FORNE Y. v FEED WATER AND STEAM HEATER FOB STEAM B0lLEBS..

(Application filed June 19,1901.)

(No Model.)

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M ATTORNEY No. 688,402; Patented Dec. 10, IQOI. ,m. u. FO'BNEY. FEEDWATER AND STEAMHEATERFOB STEAM BOILERS (Applicatian flledJuna 19,1901.)' (No Model.) l5 Sheets$haet 8;

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No. 688,402. Patented 1m. 10, I901,

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FEED WATER AND STEAM HEAT-EB FOB STEAM BOILERS; App1ica.tion filed June19, 1901.) (No Model.) l5 Sheets-Sheet 9.

WIT'NESSESL ATTORNEY m: yoams PETERS cov. vuoroumou WASHINGTON n, c.

v Patented Dec. l0, I901; m. N. oam-:v. FEED WATER AND STEAM HEATER FORSTEAM BOILERS.

v (Application filed June 19, 1901.) (No Model.)

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WITNESSES: 7/7 INVENITOR I f v 4/0 ATTORNEY ms FEIERS coy. Pnommum.wnsrlmn'wm 041:,

Patented Dec. I0, I91.

.M; N. FORNEY. FEED WATER AND STEAM HEATER FUR STEAM BOILERS.

(Application meg June 19, 1901.

' l5 Sheets-Sheet II. v

(No Model.)

' T I .TTH

Patented Dec. 10-, I901. M. N. FURNEY; FEED WATER AND STEAM HEATER FORSTEAM BOILERS.

(Application filed June 19, 1901.)

I5 Sheets$heet l2.

(No Model.

ATTORNEY Patents d Bee. in, l90l.

,m. u. FURNEY v FEED WATER AND STEAM HEATER FOB STEAM BOILERS.

(Application filed June 19, 1801.)

I5 Sheets-Sheet l3.

(No Model.)

WITNESSES n1: Norms Pmls no. wwournoq wnsmuam No."688, 402. PatentedDec. l0, I901.

M. N. FURNEY.

FEED WATER AND STEAM HEATER FOB STEAMBUILEBS.

(Application filed June 19, 1901.3

I5 Sheets-Sheei I4.

(No Model.)

WITNESSES:

Y E N R 0 T T A M. N. FURNEY. FEED WATER AND STEAM HEATER FOB STEAMBOILERS.

Patented Dec; I0,'*'I90l. (Applicaiion filed. Tune 19, 1901.)

I5 Sheets-Sheet is.

(No Model.)

FIGZS.

WITNESSES n45 uunms PETERS c0. Puufauma. wnsnlumuu. n. c.

" U ITED STATES i PATENT OFFICE.

MATTHIAS N. FORNEY, OF NEW YORK, N. Y.

l-EED-WATERAND STEAM HEATER FOR STEAM-BOILERS.

SPECIFICATION forming part of Letters Patent No. 688,402, dated December10, 1901.

Application filed J' 11113 19, 1901.

To Kill whom it witty concern:

Be it known that I, MATTHIAS N. FORNEY, of the borough of Manhattan, inthe city and State of New York, have invented a certain new and usefulImprovement in Feed-Water and Steam Heaters for Steam- Boilerspf whichimprovement the following is a specification.

My present invention relates more particularl y to feed-wateror steamheaters for steamboilers of the locomotive type; but it is alsoapplicable to boilers of other forms. Its objects are to provide meanswherebythe exhaust-steam after it escapes from the cylin-. ders willimpart a portion of its-heat to the feed-water before thefeed-waterenters the boilerand also means whereby a portion of the heat from theproducts of combustion,

which ordinarily escapes-from the boilertubes and passes out of thechimney, will be communicated to the feed-water before it enters theboiler or to the steam before it enters the cylinders; also, means bywhich the prodnets of combustion may bemade to circulate in contact withtubes containing or surrounded by the feed-water or steam to be heatedor may be conducted directly from the boilertubes to the chimney; also,appliances in operative combination with the heater-tubes forcollecting'cinders and sparks and discharging them when steam is shutoff from the comotive; also, mechanism for readily removing a coil ofpipes or other appliances for heating feed-water or steam from thesmokebox to repair or clean it; also, means which will permit of adifference in the'expansion or contraction of the tubes in which thewater is heated and of. the inclosures in which they are contained.

To these ends my invention, generally stated,consists in certain novelcombinations, hereinafter set forth, comprising an exhaustheater inwhich the feed-water is heated by the exhaust-steam, said heater havingachamber or chambers placed, preferably, in proximity to the smoke-boxand a plurality of tubes which either contain or are surrounded by thefeed-water and through oraround which the exhaust-steam may circulate,saidchambers and tubes being soconstructed as to permit of a difierenceof expansion or contraction between the tubes and the inclosure in whichthey are contained, partitions be- 'other the fire-heater.

Serial No. 65,209. (No model.)

ing provided in said chambers to cause the water to circulatesuccessively through all the tubes and external openings and'removablecovering-plates opposite the ends of the heating-tubes and communicatingwith and giving access to them; a fire-heater in which the water isheated by the smoke and gases from the fire after they have passedthrough the boiler-tubes, said heater having a plurality of tubesthrough or around which waste products of combustion may be passedbefore being discharged into the chimney and around or through whichfeed-water may be circulated; means for supplying feed-water to theexhaust-heater; a conduit for the transfer of feed-water from theexhaust-heater to the fire-heater; a conduit for the delivery offeedwater from the fire-heater to the boiler; a de vice for controllingthe traverse of'waste products of combustion either directly to thechimney or intermediately through the fireheater; a receptacle for theretention of solid products of combustion after their separation fromsmoke and gases in passing through the fire-heater; a device fordischarging solid matter from said receptacle, and a device foreffecting the removal and replacement of the fire-heater from thesmoke-box for purposes of cleaning or repair.

Before proceeding with a detailed description of my improvement itshould be understood that in all the plans shown the feedwater is heatedin two stagesfirst by the exhaust-steam and next by the waste gases andproducts of combustion. For clearness and brevity, therefore, the heaterin which the exhaust-steam is used as the agent for heating will becalled the exhaust-heater and the These two heating appliances may beused separately, but the max-imumadvantageous results may be attained bycombining them. Thefire-heater or a portion of it may be employed forsuperheating the steam after it leaves the boiler and before it entersthe cylinders or in compound engines for reheating it in its passagefrom the high to the low pressure cylinders.

The fire-heaters which I have devised consist of a plurality ofheating-tubes which are contained within or are in proximity to thesmoke-box. These either contain or are surrounded by the feed-water orsteam' to be heated, and the waste gases from the boiler before theyescape out of the chimney are caused to circulate through or aroundthese heater-tubes. The feed-water is first heated in the exhaust-heaterand is then delivered into the fire-heater, in which an additionalamount of heat is imparted to it by the waste gases of combustion. Theheating-tubes of the fire-heater, which contain water, are also providedwith covering-plates opposite to the ends of the tubes, so as to giveready access to them for cleaning and repairs.

My invention further comprehends a partition or diaphragm in thesmoke-box provided with a door or valve by which the lower portion ofthe smoke-box may be separated from the upper part, and the products ofcombustion may thereby be conducted through or around the tubes of thefire-heater, or when said door is opened the smoke and waste gases mayescape directly out of the chimney. The purpose ofthis device is tolessen the obstruction to the draft caused by the circulation of theproducts of combustion through or around the heating-tubes, and thuspermit the full power of the exhaust-steam blast to be exerted on thefire when it is required. The fire-heaters herein described might,however, be used without such a partition or without a door or valveconnected to it.

In the form of fire-heater herein described, Figures 1 to 7, in whichthe heating-tubes are surrounded by instead of containing the feedwater,the smoke and gases pass from the lower part of the main smoke-boxthrough the lower heater-tubes and return through the upper ones to theupper section of the smoke-box and thence to the chimney. In other formsthe heating-tubes contain the water to be heated and are all providedwith external openings and covering-plates opposite to their ends, whichcan readily be removed to clean and repair the tubes, and suitablepartitions are provided at their ends to cause the water to circulatesuccessively through the tubes. A receptacle for sparks and cinders isalso provided with a door for discharging, them, as will hereinafter bemore fully described.

In the accompanying drawings, Fig. 1 is a side view of the front end ofa locomotiveboiler, showing the smoke-box and the front part of theboiler-shell which incloses the boiler tubes and illustrating one formof my invention. Fig. 2 is a longitudinal central section through thesame; Fig. 3, a vertical transverse section looking forward, theright-hand half being taken on the line a a and the left-hand half onthe line b b of Figs. 1 and 2; Fig. 4, a half end view of theexhaust-heater with the cover removed looking in the direction of thedart c; Fig. 5, a halfsectional view of the other end of this heater,taken on the line 6 eand looking in the direction of the dart (1; .Figs.6 and 7, sectional and plan views, respectively, on an enlarged scale,of the covering-plates and their fastenings at the ends of the tubes.Fig. 8 is aviewin side elevation of the front end of a locomotiveboiler,showing steam and exhaust heaters, each of which has straight transversewatertubes disposed somewhat diiferently from those in the precedingfigures; Fig. 9', averti-' cal section of the end of the exhaust-heater,taken on theline ffof Fig. 14; Fig. 10, asimilar section of thefire-heater drawn on the line 9 got Fig. 14; Fig. 11, alongitudinalcentral section through the front end of the boiler and the heaters;Fig. 12, a section, and Fig. 13 a plan, of one of the tube-coveringplates and their fastenings drawn on an enlarged scale; Fig. 14, avertical transverse section through the smoke-box and heaters of Figs. 8to 13, inclusive, looking backward, the upper righthand siderepresenting a transverse section of the smoke-box drawn on the line It72 of Figs. Sand 11, the npperleft-hand side beinga section of thefire-heater drawn in the linet'i of Figs. 8 and 11, and the lower partof this figure being a section representing the whole of theexhaust-heater; Fig. 15, a sectional plan of the exhaust-heater, theright-hand half drawn on the line 7.; 7t" and the left-hand half on theline Z Z of Fig. 14. Figs. 16 to 19 illustrate a form of heater in whichtubes are arranged vertically and in which the same tubes form both theexhaust and the fire heaters. Fig. 16 is an external side view; Fig. 17,a longitudinal central section; Fig. 18, a vertical transverse sectionlooking backward, the right-hand half being taken on the line m m ofFigs. 16 and 17 and the left-hand side on the line it n of the samefigures; Fig. 19, a sectional plan view, the right-hand half being insection on the line 0 0 of Fig. 18 and the left-hand half a plan view,looking down on the top of the fire-heater, with the outside top coverremoved. Figs. 20 to 23 illustrate a fire-heater having its tubes placeddiagonally and an exhaust-heater having curved tubes similar to thoseshown in Figs. 1 to 5. Fig. 20is a longitudinal central section, and.Fig. 21 a vertical transverse sect ion, through both heaters, theright-hand half of Fig. 21 being taken on the linepp and the left-handhalf on the line (1 q of Fig. 20 looking forward; Fig. 22, a half endview with the outside cover removed, and Fig. 23 ahalf-section on theline 77Of Fig. 21 looking at the ends of the heating-tubes. Fig. 24 is aside elevation, and Fig. 25 a longitudinal section, of the smoke-box andadjacent parts of a locomotive-boiler, showing a fire-heater havinghorizontal longitudinal water-tubes and an exhaust-heater having curvedtransverse tubes; Fig. 26, a plan view of the crane from which thefire-heater is suspended and by which it is removable from thesmoke-box; Fig. 27, a vertical transverse section, the right-hand halfbeing taken on the line 3 s and the left-hand half on the line ttof Fig.25 looking forward; Fig. 28, a haltsection on the line 0 v of Fig. 27looking at the ends of the heating-tubes of the exhau heater in thedirection of the dart w;

to which the heating-tubes are attached, be

ing shown in section; and Fig. 30, an end View of one-half of theexhaust-heater looking'in'the direction of the dart ac and with theoutside cover removed.

The main object of 'myinvention is, as before stated, to utilize aportion of the heat which is carried away by the exhaust-steam and alsoa part of that contained in the waste gases of combustion to heat thefeed-water or thesteam. The appliances herein described are also adaptedfor superheatin g orreheating steam.

In feed-water heaters which have heretofore been essa'yed on locomotivesthe following difficulties havebeen encountered: First, there has beeninsufficient heating-surface, so that the water was only slightlyheated;

second, the tubes or other receptacles which contained the feed-waterhave been quickly clogged withsolid deposits from the water,

which could not be readily removed from them; third, there was aninadequate provision for the expansion and contraction of the tubes,which caused leakage and was destructive to the apparatus, and, fourth,the various parts were more or less inaccessible, and thereforedifficult-to repair or renew. By my present invention, as alreadystated, the water is heated in two successive stagesfirst by theexhaust-steam andnext by the waste gases of combustion-as described inLetters Patent No. 632,708, granted andissued to me under date ofSeptember '12, 1899.

In order to provide an ample amount of in set forth, excepting one ofthem, the Water is contained in the inside of tubes and the heatingmediums-that is, the exhaust-steam and waste'gasesare applied totheoutside. These tubes are then all so disposed that their insides areaccessible from their ends and from the outside of the locomotive, andthus any accumulated mud or deposit can readily be removed. The ends ofthe tubes can also be calked from the outside if they should leak, orany tube can be removed and replaced byanew one, if it is required to doso, without disturbing any other part. Several diflerent means areemployed to provide for the expansion and contraction of the tubes,which with the construction devised for making the different partsreadily accessible for cleaning and repairs will be hereinafterexplained. As it may also be desirable at times to apply the full forceof the blast to stimulate the fire and permit the products of combustionto flow directly from the boilertubesto the chimney without circulatingin contact with the surfaces of the tubes of the fire-heater, a door orValve is provided inside of the smoke-box, which when raised 'up into avertical position allows the smoke and gases from the boilertubes toflow directly upward and out of the chimney. When the door is lowered,the smoke-box is divided into an upper and a lower chamber, and thecourse of the gases is intercepted and they are directed and made toflow from the lower partof the smoke-box through or around the tubeswhich provide the heating-surfaces of the fire-heater and thence intothe upper part of the smoke-box to the chimney. Suitable means areprovided for opening and closing this doorfrom the cab of thelocomotive. One of the effects of the circulation of the products ofcombustion in contact with the surfaces of the heater, which will becomparatively cool, is that the incandescent sparks and cinders will beextinguished and their movement being arrested bysuch contact they willfall and be deposited in the lower part of the smoke-box. In view ofthis I have provided a receptacle into which they will be carried by theaction of the draft and in which they will be retained while thelocomotive is working steam.

A doorhavin g a counterweight is provided at the bottom of thereceptacle. When the receptacle is empty, this door is closed by theweight, and when the locomotive is working. steam a pressure is exertedon the under side of the door by reason of the partial vacuum producedby the steam-blast in the smokebox, and the door is thus kept closed solong as the locomotive is working steam; but as soon as this is shut offand there is no longer a partial vacuum in the smoke-box nor anycleaning, to facilitate cleaning, and also to give access to thesmoke-box for repairs, a form of fire-heater, .Figs. 24 to 28,inclusive, is provided which is readily removable from the smoke-box bymeans of a species of crane which supports the heater when it isdetached from the smoke-box and by which it can be removed therefrom andreplaced therein,thus

tion circulate about the outside of them.

permitting the heating-tubes to be readily cleaned and giving fullaccess to them and to the smoke-box for making repairs.

To accomplish the ends above described, various dispositions of systemsof heatingtubes are provided, all embodying the essential andcharacteristic features of my invention. As explained, those for thefire-heater are placed inside of the extended smoke-box and those forthe exhaust-heater below such extension, and all are located ahead ofthe cylinders, exhaust-pipes, and chimney, although this is not anessential feature of the invention, and are disposed in a variety ofways, as shown by the drawings.

Figs. 1 to 3, inclusive, represent the fireheater as provided withhorizontal longitudinal tubes 5 5 and 7 7, which are surrounded withwater and through which the products of combustion pass. Theexhaust-heater 26 26 is located below the fire-heater and consists of asystem of curved tubes 27 27 27, Fig. 3, inclosed in a shell 26 26, theform of which is shown in section in Figs. 2 and 3.

The exhaust-heater (shown in Figs. 1 to 5, inclusive) is connected tothe exhaust-passages 21 of the locomotive by two pipes 22 22, whichallow the exhaust-steam to flow from the former directly into theheater, where it comes in contact with the heating-tubes 27 27 27. Thefeed-water is delivered into the exhaust-heater by a pipe 30, Figs. 1and 3. The direction of the flow of water into and through this heateris indicated by the arrows in Figs. 1, 3, and 5. The water from theexhaust-heater is delivered into the fire-heater through the opening 35,Fig. 3. In Figs. 8 to 15, inclusive, both the exhaust and fire heaterare shown as having straight horizontal transverse tubes with the waterinside of them, and the exhaust-steam and products of combus- In Figs.16 to 18, inclusive, vertical water-tubes are shown, which extendthrough and are common to both the exhaust and fire heaters.

As shown in Figs. 20 and 21, the exhaust-v heater has curved tubessimilar to those in Figs. 1 to 3, and the fire-heater has diagonalintersecting water-tubes, and in Figs. 24 to 29, inclusive, theexhaust-heater also has curved tubes similar to those shown in Figs. 1to 3 and 20 and 21. The fire-heater (shown in Figs. 24 to 29, inclusive)has horizontal longitudinal water-tubes which are connected to cast-ironheaders at the front of the extension of the smoke-box and form a coilthrough which the feed-water flows. As before stated, a species of crane(shown clearly in Figs. 25 and 26) is provided on top of the extensionof the smoke-box. By means of this crane this system of pipes can beremoved from and replaced in the smoke-box. In all these examples thesystem of fire-heatertubes is placed ahead of the ordinary smoke-box 10,and a door 1, which is attached to a horizontal shaft 2, is provided.The shaft extends through the sides of the smoke-box and has an arm 3 onthe outside. A rod 3 connects this with the cab of the locomotive, andthe door can thus be opened and closed by the engineer at any time. Whenit is closed down in the position in which it is represented in thediflerent figures, the smoke and gases from the boiler-tubes are made tocirculate through or around the heating-tubes of the fire-heater, asshown by the arrows in Figs.

2, 11, 17, 20, and 25, before escaping out of the chimney. When the dooris raised up into the position represented by the dotted lines in thesefigures, the smoke and gases can pass directly from the boiler-tubes toand out of the chimney. This feature is common to all of the plans shownin the drawings, although the location and disposition of heatingtubesvaries in the different plans. haust-heaters in allof them consist of avessel or receptacle for the exhaust-steam which is traversed by asystem of heating tubes through which the feed water circulates. Theseheaters in the examples shown are located below the extended smoke-boxand the fire-heater; but other locations for them are available. All theheating-tubes which contain feed-water are provided with covering-platesopposite their ends. These plates are removable from the outside of thelocomotive. They give access to the inside of the tubes, which can thusbe reached for cleaning, repair, removal, and replacement.

The different forms of heaters herein proposed Will now be more fullyexplained.

In Figs. 1 to 7, inclusive, a fire-heater is represented, which consistsof a cylindrical shell 13, whose outside surface is coincident with theform of and is attached to the front end of the smoke-box 10 byangle-iron flanges 23 and bolts. Two tube plates or heads 24 25, Fig. 2,extend across and are secured to the shell 13 at or near its ends, andthe whole of the interior space of the heater is occupied byheating-tubes 5 5 7 7, which are placed the same distance apart as theboilertubes 4 4, but the heater-tubes are of larger diameter than theboiler-tubes. The space around the heater-tubes is filled with thefeed-water. The exhaust-heater in this plan consists ofa vessel 26, thetransverse section of which is shaped to conform to the outer contour ofthe smoke-box, as shown in Fig. 3, and also to be adapted to receive thebent tubes which it contains. This form of heater allows a larger numberof tubes to be used in the available space which can be occupied by' theheater than any other form would, and

the bent form of the tubes permits them to The exlarged scale in Figs.,6 and 7. Each of them is fastened in its position by a clamp 31, Fig.

6, which engages with the inside of theplate towhich the hand-hole coveris attached and is held bya bolt 31, (clearly shown in the drawings,)which screws into the hand-hole cover 29. The latter has a groundsurface where it is in contact with the plate to which it is fastened.By simply unscrewing the plate from its bolt it can be removed,andaccess may then be had to the inside of the tube opposite to it.

There is a space of a few inches wide between the plates, through whichthe feed-water circulates. This is conveyed from the boilerfeederthrough a pipe 30. (Shown in Figs. 1, 3, and 5.) From this pipe thewater enters a passage-way 30, Fig. 5, and flows down ward, as indicatedby the arrows, into a space 30 between the two plates of the adjacentheader 28. The space between the two plates of each of the headers isdivided by a partition 32, Fig. 5, which causes the water to circulatefirst through the lower series of tubes 27, as shown by the arrows inFig. 3. 1t flows through these tubes in the direction of the arrowsshown on the left sideof Fig. 3 into the chamber 33 of the header 28 atthe opposite end of the heater. In this the current of water isreversed, and it flows back through the tubes 27, as indicated by thearrows, to the header 28 at the opposite end of the heater, adjacent tothe pipe 30, in which header the current is again reversed and passesthrough the tubes 27 to the chamber 34 of the header at the oppositeend, from which it passes into the fire-heater through the passage 35.Exhaust-steam is conveyed from the exhaust-passages 21 by pipes 22,

which connect the former with the exhaustheater 26. Thelatter isprovided with a manholeand cover 36 on its under side to give access toits interior. A cock or valve 37 is attached to the cover to allow thecondensed water of the exhaust-steam to escape.

If the heater was filled with. air, it might to a very great extentprevent the exhaust-steam from entering or coming in contact with theheating-tubes. For this reason a pipe 38 (see Fig. 2) is provided toallow the air in the.

heater to escape. with the receptacle 16 for sparks.

This pipe is connected After all the air in the heater has beendischarged exthat is, they must pass forward through the lower series ofheating-tubes 5 of the fireheater into the supplementary smoke-box 6. Asthe effect of the blast is to produce a partial vacuum in the upper partof the smoke- '11, as indicated by the arrows.

'b0x,the contents of the supplementary smokebox 6 will be drawn backwardinto the upper part of the main smoke-box 10, through the upper tubes 7of the heater, and will then be carried upward and out of the chimney Asit is essential that there should be sufficient -secthrough them freelyand as in a heater of this kind all the smoke and gases which passthrough the boiler-tubes must pass through one half of the heater tubesand return through the other half, it is essential to provide as many ofthem and make them of as large a size as possible. As no steam will begenerated in the heater, there need not be any room provided in it forsteam, nor is it requisite to make any provision for the escape of steamfrom the tubes. Therefore the whole of the cylindrical portion or shell13 of the heater is filled with tubes and with water. The centers of thetubes are placed directly opposite those of the boiler-tubes 4:, and inorder to make it possible to remove any of the latter withoutdisturbance to the heater the heater-tubes are made of sufficientinternal diameter, so that the boiler-tubes will pass through them, andthe latter can thus be removed through the former and new onessubstituted. The heater-tubes being of enlarged diameter have each agreater sectional area than the boiler-tubes, and although there will beless free water-space between them if the tubes are enlarged this is notof much importance in a heater, because no steam is generated in it, andtherefore, as has been explained, it is not requisite to provide room ormeans for its escape from the heating-surfaces. By making the tubes inthe heater larger than the boiler-tubes and spacing both the samedistance apart and making the di ameter of theheater somewhat largerthan that of the boiler, so that the total number of tubes in it can beincreased, the internal sectional area of one-half of the heater-tubeswill, be nearly or quite as large as that of all the boiler-tubes. Asthe smoke and gases pass first through the lower series of heatertubesand then return through the upper ones,

the products of combustion have a double run through the heater-tubes,and thus the period of contact of the escaping smoke and gases with theheater-tubes is doubled,whicl1 facilitates the transmission of the heatthat they contain to the water by which they are surrounded. When thefeed-water is delivered into the exhaust-heater, as described, it willbe heated to a temperature approximating to that of the exhaust-steam,which is about 240. It will then come in contact with theheating-surfaces in the fire-heater, which are exposed to the wasteproducts of combustion that escape'from the boiler-tubes. Thetemperature of these varies between wide limits; but experiments haveshown that they are sometimes as high as 1,200". Consequently if IIO

